Note: Descriptions are shown in the official language in which they were submitted.
CA 02203~89 1997-04-24
A Circular Saw Blade and a Method of Manufacturinq Same
FIELD OF THE INVENTION
The present invention relates to the field of circular
saw blades, in particular to circular saw blades used for
sawing wood.
More specifically, the invention is concerned with a
circular saw blade comprising a flat annular member being
provided with teeth at a periphery thereof, the flat annular
member having a frusto-conical shape.
Still more specifically, the invention is related to a
method of manufacturing a circular saw blade comprising pro-
viding a plane, flat annular member having teeth at a periph-
ery thereof, wherein the method comprises rolling the flat
annular member.
BACKGROUND OF THE INVENTION
U.S. patent specification 5,323,670 of the same appli-
cant discloses a circular saw blade as used for sawing, sepa-
rating or slotting wood or, under a more general aspect, for
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working on rigid materials having a modulus of elasticity of
preferably between 50,000 through 400,000, in particular
100,000 through 160,000 kg/cm2, where the saw blade has a
cutting speed in excess of 40 m/s for providing a slot of
finite width. Circular saws of the kind specified before are,
for example, used for profiling logs, in particular for sepa-
rating so-called lateral boards from the remaining center
portion of the log.
The circular saw blade of U.S. patent specification
5,323,670 comprises an assembly of a carrier member having a
central opening for receiving a drive shaft of a conventional
circular saw. The carrier member is configured as a toroidal
element and is shaped frusto-conically at the periphery of
its lower surface. A relatively thin annular blade is
attached to the carrier periphery, wherein when the blade is
bolted against the conical or hollow-conical surface, it is
automatically converted into a frusto-conical shape. The
taper angle is of the order of between 0,1~ and 1~. When the
circular saw blade has a total diameter of the order of
700 mm, the afore-mentioned taper angle results in an overall
height of the taper at its axis of between 0.6 and 6.0 mm.
For manufacturing the prior art circular saw blade, the
thin blade is first produced in a plane shape. The blade is
then rolled along circles being concentric to the axis of
rotation.
The rolled blade, having still a plane shape during this
step of the manufacturing process is then bolted against the
conical or hollow-conical surface of the carrier member.
During the bolting the shape flips from its plane shape into
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the hollow-conical shape corresponding to the carrier member
counter surface.
The prior art saw blade has an annular projection on its
surface, the projection being radially inside the peripheral
saw blade teeth. In a radial sectional view the projection
has a triangular cross section. The projection, hence, has a
leading edge facing the blade periphery since the projection
becomes thicker in a direction towards the axis of rotation.
On its backside, i.e. on the radially inner side, the projec-
tion is provided with a stepped transition. This stepped
transition is adapted with a m;niml~m clearance to a station-
ary deflection or separation element having also a toroidal
shape and being arranged concentrical with respect to the
carrier member.
By doing so the boards being separated from the log by
means of the peripheral teeth first come into contact with
the leading edge of the projection and are then guided over
the transition to the stationary separation element, thus re-
ducing friction between the rotating saw blade and the sepa-
rated board. It is well known to make the angle of the sepa-
ration element such that the front end of the separated board
will come into contact with the leading edge of the projec-
tion only during the first contact because after the front
end of the separated board running on the separation element,
the board is lifted off the projection so that the separated
board bridges the distance between the teeth and the separa-
tion element without any further contact with the projection.
In the practice of the manufacture of these prior art
saw blades one has become aware that the rolling step may be
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optimized by rolling on a radius of the saw blade being
essentially the same as the radius of the projection.
However, if the prior art circular saw blade were rolled
along the projection, one would be faced with the following
two disadvantages:
First, it presents a technical problem to roll a work-
piece along a periphery if the corresponding rolling tool
rolls on an inclined surface or comes in contact with a sharp
edge of the projection located between the inclined leading
edge and the essentially axial stepped transition.
Further, it is necessary to configure the blade in the
rolling area sufficiently thick in order to be able to absorb
all of the forces as exerted on the blade during rolling.
For, if the exerted rolling forces are too big or the blade
is too thin, one runs the risk that the blade will break in
the area of its teeth during rolling.
Insofar, one has to bear in mind that it is always an
object to make the blade as thin as possible because only a
thin blade results in a narrow cutting gap and, hence, to a
high efficiency in the exploitation of the wood volume
because only a minimllm fraction of the wood is converted into
saw dust.
It is, therefore, an object underlying the invention to
improve a circular saw blade and a method as specified at the
outset such that even very thin circular saw blades may be
rolled while using big rolling forces.
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SUMMARY OF THE INVENTION
These and other objects are achieved according to the
invention by a circular saw blade comprising a flat annular
member being provided with teeth at a periphery thereof, the
flat annular member having a frusto-conical shape with an
inner surface and an outer surface, an annular projection
being provided on the outer surface and being disposed radi-
ally inside the teeth, the projection having a surface, the
surface being configured as a flat plateau.
Further, the object is achieved by a method of manu-
facturing a circular saw blade comprising the steps of:
- providing a plane, flat annular member having teeth
at a periphery thereof, the flat annular member having a
plane lower surface and a plane upper surface;
- providing an annular projection on the plane upper
surface radially inside the teeth; and
- rolling the annular projection to form a flat
plateau surface thereon.
The invention, hence, envisages to broaden the circular
saw blade in a radial area, hence generating a rolling sur-
face allowing to exert high forces and, hence, tensions on
the circular saw blade without generating an uncontrolled
distribution of forces and tensions. By appropriately dimen-
sioning the projection, one can even make it possible to
manufacture the saw blade with one rolling step only by opti-
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mizing same with respect to the subsequent transformation of
the saw blade shape from a plane into a frusto-conical shape.
Therefore, the invention does not necessiate to roll the saw
blade in the very thin area outside the annular projection
where the teeth are located and where the necessary plastic
deformation of the saw blade may no more be obtained in view
of the very thin cross section of the saw blade material and
without taking the risk of breaking the blade.
According to a preferred embodiment of the circular saw
blade of the invention, the plateau has a radial width being
three to ten times, preferably six to seven times, as large
as the axial thickness of the annular member body radially
outside the projection. Further, it is preferred when the
axial thickness of the projection is one to three times,
preferably one to two times, as large as the axial thickness
of the annular member radially outside the projection.
Furtheron it is preferred when the outer radius of the
plateau is between 70 % and 90 %, preferably between 80 % and
90 % of the cutting circle radius of the teeth.
These dimensions have turned out to be particularly pre-
ferred for conventional materials of saw blades with the
further dimensions mentioned at the outset.
In a preferred embodiment of the method of the invention
the flat annular member is bolted against a concentric
carrier member having a frusto-conical shape whereby the
plane flat annular member is converted into a frusto-conical
flat annular member.
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This measure has the advantage that the taper angle may
be exactly defined and reproduced.
Further advantages may be taken from the description and
the enclosed drawing.
It goes without saying that the features mentioned
before and those that will be explained hereafter may not
only be used in the particular given combination but also in
other combinations or alone without leaving the scope of the
present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
A preferred embodiment of the invention is shown in the
drawing.
Fig. 1 shows a detail of an embodiment of a circular saw
blade according to the invention; and
Fig. 2 is a sectional view along the line II-II of
Fig. 1 in substantially enlarged scale.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
In Fig. 1 reference numeral 10 designates a circular saw
blade of the kind as described in U.S. patent specification
5,323,670 or in Canadian patent specification 1,296,602 en-
corporated herein by reference. Further details of the circu-
lar saw blade may be taken from the afore-referenced cita-
tions.
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Circular saw blade 10 comprises, inter alia, an annular
member 11, being bolted on an annular carrier body having a
conical or hollow-conical surface (not shown) when the circu-
lar saw blade 10 is assembled. It goes, however, without say-
ing that the circular saw blade 10 may also be used without
any such carrier body, i.e. consists only of annular mem-
ber 11. As an alternative, it is also possible to integrate
annular member 11 with any appropriate carrier body.
Annular member 11 has a radial inward region 12 being
axially thicker and has a radially outward region 13 being
axially thinner. A mounting bore is provided within the cen-
ter of thicker region 12. Mounting bore 14 may be used for
receiving a drive shaft of a conventional circular saw. The
axis of circular saw blade 10 is designated by 15. For the
sake of clarity further mounting bores as used for bolting
circular saw blade 10 on a carrier body (not shown) are not
shown.
The periphery of circular saw blade 10 is provided with
teeth of conventional configuration. In Fig. 2 reference
numeral 17 indicates a stationary deflection element being
likewise configured as an annular body. Deflection element 17
allows to bend separated lateral boards away from the cutting
plane, as indicated by arrow 18. The separated lateral board
is thus brought out of contact with rotating circular saw
blade 10.
A projection 20 is provided on annular member 11 along a
circumference inside teeth 16. Projection 20 has a radial
outer leading edge 21 having a flat angle of inclination.
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Projection 20 on its upper side is configured as a flat
plateau 22. On its radial inner side plateau 22 terminates in
a stepped transition 23 being directed axially inwardly.
Stepped transition 23 is designed to snugly fit to detection
element 17 with as little clearance as possible.
As indicated by an angle a the lower side 30 of annular
member 11 has a hollow-concial shape when lower side 30 is in
its assembled condition. Angle a may be between 0.1~ and
about 1~, as mentioned above.
In Fig. 1 the cutting circle radius of teeth 16 is iden-
tified by rl whereas the radius of the edge at the transition
from leading edge 21 to plateau 22 is designated by r2. The
radial width of plateau 22 is B, the thickness or elevation
of projection 20 over annular member 11 is D. The thickness
of annular member 11 radially outside projection 20 is desig-
nated by d.
In a preferred embodiment of the invention the cutting
circle radius rl is, for example, 350 mm. Thickness d is in
the order of 1.5 mm.
Starting from these absolute values it is a preferred
embodiment of the invention when the radial width B of
plateau 22 is about three to ten times as large, preferably
six to seven times as large as axial thickness d. With the
given absolute values radial width B may, for example, be
10 mm.
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- 10
Axial thickness D of projection 20 above annular member
11 may be one to three times as large, preferably one to two
times as large, as axial thickness d of annular member 11 in
preferred embodiments of the invention. With the given abso-
lute values, axial thickness D may, for example, be 2.5 mm.
Finally, the radial position of projection 20 is pref-
erably selected such that outer radius r2 ~f plateau 22 is
between 70 % and 90 %, preferably between 80 % and 90 %, of
cutting circle radius rl. With the given absolute figures
radius r2 may, for example, be 300 mm.
For manufacturing circular saw blade 10 according to the
invention, one may proceed in various ways:
In preferred embodiments of the invention circular saw
blade 10, as mentioned above, comprises a rigid mechanical
carrier body as well as a separate annular member 11. Annular
member 11 is manufactured as a plane element together with
the described broadened projection. After rolling annular
member 11 along projection 20, annular member 11, still
having a plane shape, is bolted against a conical or hollow-
conical surface on the separate carrier body. During bolting
annular member 11 flips from its initial plane shape into the
desired hollow-conical final shape.
If, according to another embodiment of the invention
circular saw blade 10 consists only of the annular member 11
of annular member 11 is configured integral with a carrier
body, the above-mentioned last method step is not required.
Instead, a conical shape of the circular saw blade is already
generated during the production of the annular member.
